1. Field of the Invention
The present invention relates to an exposure system used to produce a semiconductor device such as an integrated circuit, a device production method, a semiconductor production factory, and an exposure apparatus maintenance method, and more particularly, to an online-controlled production system used in a production line including a set of semiconductor production apparatuses including an exposure apparatus, a resist coater, and a developing apparatus which are connected to a host computer for controlling these apparatuses in a centralized manner.
2. Description of the Related Art
In a processing flow using a conventional exposure system including a combination of an exposure apparatus and a wafer processing apparatus (e.g., a resist coater and a developing apparatus), a preparation-for-exposure process (such as resist coating and pre-baking) is first performed by the wafer processing apparatus, in preparation for exposure of a wafer, and then, the wafer is exposed by the exposure apparatus. At the beginning of a lot or at a transition between lots, the exposure apparatus waits for a wafer without performing any processing until the wafer processing apparatus completes the preparation-for-exposure process.
It is required to periodically perform a maintenance process on the exposure apparatus to correct errors of various units thereof. The maintenance process is usually performed immediately before the exposure process.
In recent years, in many cases, the production line must be flexible to produce small numbers of various types of devices, and thus, the exposure system must have high productivity when used in such a production line.
The maintenance process includes a calibration process of various items such as baseline calibration and focus calibration. The calibration process must be performed for every fixed number of wafers (or in fixed intervals) to correct errors caused by time-varying environmental parameters (e.g., atmospheric pressure, temperature, etc.) or caused by the exposure apparatus itself. To minimize the time-varying factors, it is desirable to perform the calibration immediately before the exposure process for a lot (i.e., at the start of a job).
In actual factories, at present, when a plurality of lots are successively produced, the exposure apparatus waits for a wafer without performing any processing when the wafer processing apparatus performs a process for transition to another lot after completing one lot or when the wafer processing apparatus performs the preparation-for-exposure process. The maintenance process is performed after a wafer, subjected to the preparation-for-exposure process performed by the wafer processing apparatus, is fed into the exposure apparatus. This causes a reduction in the operation efficiency, which can cause an undesirable problem, in particular, when small numbers of various types of devices are produced. Furthermore, the time for the maintenance process including the calibration process causes a throughput reduction which cannot be ignored.
To meet the needs for production of small numbers of various types of devices, the production line is expected to have to more frequently perform processing for a lot including only one wafer. Thus, a requirement is to improve the operation efficiency and the total throughput.